The planetarium will be closed for upgrades Sep. 6–Oct. 20. Details.
The third Thursday of every month, the Morrison Planetarium hosts “Universe Update” at the 6:30 planetarium show during NightLife. Normally, our director Ryan Wyatt selects his favorite astronomy stories from the past month, but this week he is away “across the pond” and I got to give a brief run-down of current discoveries while taking audiences on a guided tour of the Universe. As you may or may not know, the planetarium sports a three-dimensional atlas of the Universe, so we can take you places virtually while talking about the latest astronomy news.
We typically start here on Earth, giving our audience a sense of scale and perspective on the realism of the data we show. When we look down onto our projected San Francisco, we can see some of the minute structure of the city—even some of the larger buildings are discernible. As we move out, however, we can see large portions of planet Earth are missing. Within our dome we show real data and the photos you see are just that, images captured by a small army (or rather air force?) of satellites orbiting our planet. They image the surface of Earth, but where there is no land, they tend to sort of skim over.
These satellites have become an integral part of our life here on Earth: from location services to LOLcats, finance to funny videos, we use this infrastructure each and every day. Yet, due to their function, some of our most critical satellites are in a geostationary orbit, placing them far from Earth’s surface and near the edge of our magnetic field.
Our planet is shielded every moment of the day from the star we orbit—a fortunate phenomenon, because our star is a fairly active midsize one, bombarding its surroundings with energetic particles and radiation. Were it not for this protective barrier, life on Earth would be in a bad way, but outside this barrier, our orbiting satellites are quite vulnerable to solar activity.
By studying our star, we have determined that although it does have an observable cycle, it is not wholly predictable. Every eleven years it experiences a solar maximum with higher numbers of sunspots and solar storms occurring, but the current maximum has been quite calm, all things considered. Solar scientists in Boulder, Colorado, just presented findings about our vulnerability to solar activity, but since the cycle has been calm, you might assume we have little to worry about…
Well, not really. Even though our sun is experiencing a mild maximum, it did have a potent event in 2012, a near miss of energetic particles that swept past Earth. Had it hit, we would have experienced stupendous auroral storms, extending the beautiful northern (and southern) lights almost all the way to the equator. What’s so bad about that? This same event could have knocked out power grids and transformers across the world. A funny thing about multi-ton transformers, they are not stockpiled anywhere, and it takes a long time and significant manufacturing capabilities to make them. If they were widely damaged, power grids could be out of commission for years.
The conclusions drawn by this panel of scientists have dire implications, but on the whole they encourage caution and a better understanding of our star—both good things!
From our position in the Solar System, the Sun is our source of heat, energy, and (everywhere but San Francisco) light. Life on Earth requires water, kept warm and liquid by the energy we receive, but farther from the Sun, this energy becomes more scarce. For a long time, planetary scientists believed that beyond the orbit of Mars, liquid water just wouldn’t exist.
By modeling the volume and mass of some of Jupiter’s largest moons, specifically Europa and Ganymede, scientists expected they would have an icy component. Ice heated by gravitational action has yielded water beneath the surface of Europa and similar conditions are now thought to exist on Saturn’s (much smaller) moon, Enceladus, but a new model of the largest known moon has emerged—and now subsurface oceans are hypothesized on Ganymede as well!
Called the “Dagwood” model, after Blondie’s husband’s unlikely sandwiches, water and various crystalline types of ice are thought to be layered in an alternating pattern. While this is certainly not the kind of ocean you would want to take a dip in, it does raise again the likelihood of waterborne life somewhere in the Universe.
Understanding where life comes from is one of those big and inestimably complex questions that we as a species are pretty hung up on, so we often search for our celestial cousins—Earth-like planets and Sun-like stars. Now, astronomers might have uncovered our sun’s lineage, given a recent discovery of a star of the same age, chemical composition, and close relative motion to our sun. This 110-light-year-distant star is thought to be our star’s “sibling,” meaning that they (and probably many others) formed from the same cloud of gas dust and material out there in the Universe. Perhaps if we can track down a few more “solar siblings,” we can trace back their trajectories and find out where in the Milky Way our star was born.
Understanding how stars move within galaxies contributes a vital part to figuring out how the galaxies themselves change and evolve over time. Astronomers use incredibly complex models to determine how the Universe has reached its current state. This requires detailed observations of star motion, galaxies of all shapes and sizes, and ideas about how even the unobservable elements of our universe behave. By feeding in the information about how our universe began and comparing the universe as modeled to the Universe we see today, we as a species have found a way to watch events unfold on a physical and temporal scale that would otherwise be impossible.
While this might seem strange and abstract when compared to sciences that focus on examining artifacts or specimens, these activities are grounded in the same ideas. The better we understand our observations, the better we can come to know how things got the way they are now.
One last exciting piece of news, which illustrates this point. Scientists observing an object orbiting the super-massive black hole that dwells within the heart of the Milky Way were thrilled to watch an astronomical event unfold in a matter of days, not centuries. They watched the creatively named “S2” object swoop past and predicted it would either be ripped apart or flung out of the area. It did neither, it kind of squished, spread out, and blatantly defied our models. But that doesn’t mean the models are wrong, it just means we can make them better.
Josh Roberts is a Senior Presenter and astronomer at the California Academy of Sciences. He also contributes to Morrison Planetarium productions and is involved in Bay Area astronomy outreach.
Image: NASA / Illustris Collaboration